For many personal care products, it is desirable not only to provide consumers the basic function of cleansing the skin or hair, but also to deposit a topically active compound that provides a predetermined benefit. The paradoxical problem of cleaning skin, or other surfaces, such as hair, cloth, or hard surfaces, while simultaneously depositing a topically active compound has been investigated for decades. Recent publications show that simultaneous cleaning and deposition of topically active ingredients is still a challenge, for example, see U.S. Pat. Nos. 5,885,948; 6,080,707; and 6,080,708.
The need for cleansing compositions that efficiently deposit topically active compounds is magnified when the typically high cost of the topically active compounds is considered, because a substantial portion of these expensive compounds is wasted in present-day compositions. In addition, particular topically active compounds, like antimicrobial agents, can provide both quick-acting and residual benefits. The value of a quick-acting antimicrobial agent is evident, and the residual benefit of antimicrobial agents is discussed in WO 98/55095 and U.S. Pat. No. 6,113,933, incorporated herein by reference.
Topically active compounds encompass a wide range of materials, including antibacterial agents, sunscreens, vitamins, medicaments, fragrance materials, antioxidants, conditioners, emollients, and other hair-care and skin-care ingredients. Many of these compounds are relatively water insoluble. Present-day compositions typically rely upon solubilization of active compounds in a surfactant system. Other systems rely upon a dispersion of emulsified active oil droplets.
A surfactant solubilized active compound is not effectively deposited unless the active compound is present at a very high level of saturation in the composition, or the active compound is chemically and/or physically modified to enhance deposition. However, there is a practical limit to incorporating a high level of saturation of active compound with traditional surfactant systems because of cost and/or regulatory constraints. For example, a composition containing 15% ammonium lauryl sulfate can require about 3% triclosan to form a saturated system. Because of the high cost of triclosan, such a composition would be too expensive to commercialize. Physical/chemical modifications of the active compounds, while possibly enhancing deposition, may not be desirable because of additional cost to an already expensive ingredient and/or the need for regulatory reapproval and additional testing required for the modified active compound.
The dispersion-type of emulsion composition typically operates by dilution deposition, and has the potential to deposit active compounds relatively well. However, this type of composition has limitations. For example, typical compositions are thickened dispersions, and cannot be used in certain dispensers (e.g., a self-foaming pump). In addition, some active compounds may not be biologically available on the skin, hair, or other surface when in the form of relatively large hydrophobic droplets or dissolved in a carrier oil.
Other strategies to enhance deposition include the addition of certain materials that enhance substantivity of active compounds by “codeposition,” i.e., a “deposition aid” which adheres to the skin or hair and purportedly enhances deposition of an active ingredient. This strategy also has a limitation of decreased bioavailability when the active compound/deposition aid complex contacts the skin or hair, because the active compound may be less prone to diffuse to the site of action and/or may not be uniformly dispersed over the treated surface.
While not being bound by theory, it is envisioned that a present composition combines two principles to enhance deposition of active compounds. The first principle is the use of high thermodynamic activity (i.e., high percent saturation) to enhance the tendency of the active compound to deposit on surfaces. Allawalla et al., J. Amer. Pharmaceut., Assn., XLII, pp. 267-274 (1953) disclose the importance of this factor of the activity of antimicrobial agents. In fact, as illustrated herein, thermodynamic activity is an important factor in enhancing deposition of other active compounds as well.
The second principle that contributes to enhanced deposition is the surprising and unique property of a present composition to release the active compound upon dilution. While the novel compositions containing an active compound, an anionic surfactant, a hydrotrope, a hydric solvent, an optional cosurfactant, and other optional ingredients form clear, mobile, phase-stable compositions, the compositions become unstable upon dilution with water and deposit the active compound to a surface in a highly effective manner. This type of behavior is in sharp contrast to typical solubilized active systems that generally remain stable upon dilution. The mechanism of deposition also is different from the dilution deposition of compositions disclosed in prior art because the present compositions do not contain dispersed oil droplets typical in existing emulsion systems.
Persons skilled in the art have evaluated numerous, diverse strategies to enhance the deposition of topically active compounds on the skin and hair. A review of these diverse strategies to solve the problem of cleaning a surface and depositing a topically active compound on the surface is summarized below. It can be seen that the present compositions are novel and nonobvious even over the art.
Compositions encompassed by the present invention include, but are not limited to, skin care, hair care, hard surface cleaning, and similar compositions used to cleanse and/or treat a surface. The present disclosure is directed primarily to antibacterial compositions, but also applies to other compositions containing a topically active compound.
With respect to antibacterial personal care compositions, such compositions are known in the art. Especially useful are antibacterial cleansing compositions, which typically are used to cleanse the skin and to destroy bacteria and other microorganisms present on the skin, especially the hands, arms, and face of the user.
Antibacterial compositions in general are used, for example, in the health care industry, food service industry, meat processing industry, and in the private sector by individual consumers. The widespread use of antibacterial compositions indicates the importance consumers place on controlling bacteria and other microorganism populations on skin. It is important, however, that antibacterial compositions provide a substantial and broad spectrum reduction in microorganism populations quickly and without problems associated with toxicity and skin irritation.
In particular, antibacterial cleansing compositions typically contain an active antibacterial agent, a surfactant, and various other ingredients, for example, dyes, fragrances, pH adjusters, thickeners, skin conditioners, and the like, in an aqueous carrier. Several different classes of antibacterial agents have been used in antibacterial cleansing compositions. Examples of antibacterial agents include a bisguanidine (e.g., chlorhexidine digluconate), diphenyl compounds, benzyl alcohols, trihalocarbanilides, quaternary ammonium compounds, ethoxylated phenols, and phenolic compounds, such as halo-substituted phenolic compounds, like PCMX (i.e., p-chloro-m-xylenol) and triclosan (i.e., 2,4,4′-trichloro-2′hydroxy-diphenylether). Present-day antimicrobial compositions based on such antibacterial agents exhibit a wide range of antibacterial activity, ranging from low to high, depending on the microorganism to be controlled and the particular antibacterial composition.
Most commercial antibacterial compositions, however, generally offer a low to moderate antibacterial activity. Antibacterial activity is assessed against a broad spectrum of microorganisms, including both Gram positive and Gram negative microorganisms. The log reduction, or alternatively the percent reduction, in bacterial populations provided by the antibacterial composition correlates to antibacterial activity. A log reduction of 3-5 is most preferred, a 1-3 reduction is preferred, whereas a log reduction of less than 1 is least preferred, for a particular contact time, generally ranging from 15 seconds to 5 minutes. Thus, a highly preferred antibacterial composition exhibits a 3-5 log reduction against a broad spectrum of microorganisms in a short contact time. Prior disclosures illustrate attempts to provide such antibacterial compositions, which, to date, do not provide the rapid, broad range control of microorganisms desired by consumers.
It should be noted that high log reductions have been achieved at pH values of 4 and 9, but such log reductions are attributed at least in part to these relatively extreme pH values. Compositions having such pH values can irritate the skin and other surfaces, and, therefore, typically are avoided. It has been difficult to impossible to achieve a high log reduction using an antibacterial composition having a neutral pH of about 5 to about 8, and especially about 6 to about 8.
For example, WO98/01110 discloses compositions comprising triclosan, surfactants, solvents, chelating agents, thickeners, buffering agents, and water. WO98/01110 is directed to reducing skin irritation by employing a reduced amount of surfactant.
Fendler et al. U.S. Pat. No. 5,635,462 discloses compositions comprising PCMX and selected surfactants. The compositions disclosed therein are devoid of anionic surfactants and nonionic surfactants.
WO97/46218 and WO96/06152 disclose compositions based on triclosan, organic acids or salts, hydrotropes, and hydric solvents.
EP 0 505 935 discloses compositions containing PCMX in combination with nonionic and anionic surfactants, particularly nonionic block copolymer surfactants.
WO95/32705 discloses a mild surfactant combination that can be combined with antibacterial compounds, like triclosan.
WO95/09605 discloses antibacterial compositions containing anionic surfactants and alkylpolyglycoside surfactants.
WO98/55096 discloses antimicrobial wipes having a porous sheet impregnated with an antibacterial composition containing an active antimicrobial agent, an anionic surfactant, an acid, and water, wherein the composition has a pH of about 3.0 to about 6.0.
N. A. Allawala et al., J. Amer. Pharm. Assoc.—Sci. Ed., Vol. XLII, no. 5, pp. 267-275 (1953) discusses the antibacterial activity of active antibacterial agents in combination with surfactants.
A. G. Mitchell, J. Pharm. Pharmacol., Vol. 16, pp. 533-537 (1964) discloses compositions containing PCMX and a nonionic surfactant that exhibit antibacterial activity. The compositions disclosed in the Mitchell publication exhibit antibacterial activity in at least 47 minutes contact time, thus the compositions are not highly effective.
Prior disclosures have not addressed the issue of which composition ingredient in an antibacterial composition provides bacterial control. Prior compositions also have not provided an effective, fast, and broad spectrum control of bacteria at a neutral pH of about 5 to about 8, and especially at about 6 to about 8.
An efficacious antibacterial composition has been difficult to achieve because of the properties of the antibacterial agents and the effects of a surfactant on an antibacterial agent. For example, several active antibacterial agents, like phenols, have an exceedingly low solubility in water, e.g., triclosan solubility in water is about 5 to 10 ppm (parts per million). The solubility of the antibacterial agent is increased by adding surfactants to the composition. However, an increase in solubility of the antimicrobial agent, and in turn, the amount of antibacterial agent in the composition, does not necessarily lead to an increased antibacterial efficacy.
Without being bound to any particular theory, it is theorized that the addition of a surfactant increases antimicrobial agent solubility, but also typically reduces the availability of the antibacterial agent because a surfactant in water forms micelles above the critical micelle concentration of the surfactant. The critical micelle concentration varies from surfactant to surfactant. The formation of micelles is important because micelles have a lipophilic region that attracts and solubilizes the antibacterial agent, and thereby renders the antibacterial agent unavailable to immediately contact bacteria, and thereby control bacteria in short time period (i.e., one minute or less).
The antibacterial agent solubilized in the surfactant micelles will control bacteria, but in relatively long time frames. The antibacterial agent, if free in the aqueous solution and not tied up in the surfactant micelle (i.e., is activated), is attracted to the lipophilic membrane of the bacteria and performs its function quickly. If the antibacterial agent is tied up in the surfactant micelle (i.e., is not activated), the antibacterial agent is only slowly available and cannot perform its function in a time frame that is practical for cleaning the skin.
In addition, an antibacterial agent solubilized in the micelle is readily washed from the skin during the rinsing process, and is not available to deposit on the skin to provide a residual antibacterial benefit. Rather, the antibacterial agent is washed away and wasted. The present invention is directed to enhancing the deposition of topically active compounds, like antibacterial agents.
As previously discussed, prior investigators have employed various strategies to improve deposition of a topically active compound on a surface. One strategy is to chemically modify the topically active compound, which is not a practical solution to compound deposition. Other investigators considered the nature of surface being treated. However, a commercially practicable composition should be useful on a variety of surfaces.
Other investigators utilized water-soluble cationic polymers as deposition aids for the topically active compound. See U.S. Pat. Nos. 3,489,686; 3,580,853; and 3,723,325, disclosing the use of polyethylenimine and the reaction product of polyethyleneimine and either ethylene oxide or propylene oxide, quaternary ammonium-substituted cellulose derivatives, and a polymer formed on tetraethylenepentamine and epichlorohydrin. Other patents and applications directed to the use of a deposition aid for a topically active compound include WO99/66886; U.S. Pat. Nos. 3,726,815; 3,875,071; 4,894,220; 6,057,275; and 6,126,954; WO99/63965; WO00/33807; WO99/63953.
Still other investigators directed attention to dilution deposition of a topically active compound. This is considered to be a primary deposition mechanism for many commercially available “two-in-one” conditioning shampoos. Dilution deposition involves the use of a topically active compound in a composition that is phase stable during storage and application to the hair, but becomes phase unstable and separates during rinsing. The additional water added to the composition during rinsing causes phase separation and deposition of the oil phase (which contains the topically active compound) onto the hair. Examples of patents relating to dilution deposition include EP 0 552 024; WO99/32079; WO99/53889; U.S. Pat. Nos. 5,981,465; 6,051,546; and 5,928,632; WO01/01949; WO99/26585; WO99/13854; WO99/62477; WO00/43984; and WO00/25739.
Other strategies used to enhance deposition of topically active compounds include varying the amount and type of surfactant in the composition, entrapping the topically active compound in a polymer matrix, utilizing separate cleansing and treatment compositions, using a wipe cloth to apply the topically active compound, and utilizing electrostatic sprays or liquid crystals. These strategies are disclosed in U.S. Pat. Nos. 5,409,695 and 5,814,323; WO00/64406; EP 0 573 229; WO00/00170; WO99/55303; WO99/13861; WO99/21532; WO99/12519; WO01/12138; and WO01/13871.
Accordingly, a need exists for a topically active composition that is highly efficacious in a short time period, and effectively deposits a topically active compound on a surface to provide residual benefits. The present invention is directed to such compositions, including antibacterial compositions and skin- and hair-care compositions.